The extension CRW marks the RAW files of various models of digital cameras from Canon. These files are generated by some SLR (DSLR) cameras.
The CRW format is the older raw data format of Canon, which was replaced by the version 2 with the extension cr2. It is based on the TIFF standard and also contains EXIF data.
The CRW files contain the unprocessed or minimally edited raw data of the image sensor. Although these RAW (raw) data are larger than the JPEG files stored by the device, they are more versatile.
These sometimes called "digital negative" raw data are excellent for post-processing such as the adjustment of the colors, correction of the exposure, suitable for sharpening or noise filter. They are indispensable for professional work or things like astrophotography.
In order to convert them into an RGB image format that can be commonly used, the data must be "developed". This means that processing steps such as interpolation and exposure as well as converting to a format such as PNG, PSD, TIFF or JPEG must be performed.
However, there is no uniform raw data format. Every manufacturer has developed his own. These proprietary and often undocumented formats can only be processed by specialized software. They can contain different data, for example in different color depths, depending on the capabilities of the sensor as well as the software integrated in the camera. Manufacturers are changing their RAW formats relatively frequently, which means that program support often needs to be adjusted. Supporting the extension is not enough if the specific camera is not supported.
Most RAW files also contain metadata with information about the image and the recording conditions, in some cases also in the EXIF or ITPC standard.
Adobe Photoshop and Photoshop Elements support a large number of cameras with the help of the free plug-in Adobe Camera RAW (ACR). Which depends on the ACR version. However, newer versions of ACR can only be used by the latest versions of the main programs.
Most often resolving problems with opening CRW files is very simple. Just install an appropriate program that supports such files. All of the listed programs support CRW files, but may vary in offered function and purpose. Some programs may be capable only of viewing contents of CRW files or offer file conversion options, but may not be capable of editing such files.
It is possible that although a compatible program has been installed on user’s system, it is not used by the system to open it. This may happen because no default application was associated with this type of files. To associate CRW files with given application, select "Open with" from drop-down menu (accessed by right-clicking on the file). Then select from the list the program or application you want to be used to open this type of file. If the Adobe Photoshop applications is not on the list, select "Browse" option in order to manually locate the directory where Adobe Photoshop has been installed.
Sometimes problems with opening CRW files may not lie with the application itself, but can arise due to other causes, such as: